LCMS Methodology - Quantifying mescaline in San Pedro (Trichocereus/Echinopsis)

There are lots of different ways you can test plants for drugs. The method we have used to quantify the amount of mescaline in Trichocereus (AKA San Pedro or Echinopsis) cacti uses an instrument that performs liquid chromatography-mass spectrometry (LCMS).

In the liquid chromatography part of this instrument, a sample is dissolved in a liquid, which is sent through a column. Different parts of the sample move through the column at different speeds, isolating specific compounds present in the drug mixture. In the mass spectrometry part of this instrument, the now separated components of the sample are turned into ions and sorted based on their mass. Measuring the mass of each ion helps generates a unique ‘fingerprint’ for each component.

To prepare cactus samples for testing in LCMS, we first had to develop and optimise a method for the LCMS machine, which involved choosing appropriate solvents, the window of time to gather data from the column, ensuring multiple analysts could repeat results using the same method, and a number of other design and validation efforts.

Once the method was complete, we were equipped to investigate how much mescaline was present in a given sample of San Pedro. To prepare a sample for analysis, 100 mg of freeze dried and powdered cactus would be weighed, extracted in 100 ml of methanol using 30 minutes of sonication, filtered and diluted. For each run we would also prepare a dilution curve of mescaline standard. The excel sheets containing the full data sets and analysis are available on Patreon.